Composition that can be used to delay the formation of gas hydrates

ABSTRACT

The present invention relates to a composition comprising: at least one co-polymer of which at least one of the repeating units comprises at least one amide function; and at least one polyether having a molecular weight (M W ) greater than 60 g·mol −1 . The invention also relates to the use of said composition for delaying, or even preventing, the formation of gas hydrates, in particular in a method for extracting oil and/or gas and/or condensates, as well as to the method for delaying, or even preventing, the formation and/or agglomeration of gas hydrates, using a composition as defined above.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the national phase of International Application No.PCT/FR2019/052562, filed 28 Oct. 2019, which claims priority to FrenchApplication No. 1860083, filed 31 Oct. 2018. The disclosure of each ofthese applications is incorporated herein by reference in its entiretyfor all purposes.

FIELD OF THE INVENTION

The present invention relates to the field of the extraction ofhydrocarbons and more particularly to the field of the additives used tofacilitate the extraction and the transportation of said hydrocarbonstowards the surface. The present invention relates very particularly toa process for inhibiting the formation of gas hydrates which arecommonly known to disrupt the flow of hydrocarbons in the pipes forextraction and transportation of said hydrocarbons.

BACKGROUND OF THE INVENTION

The extraction of hydrocarbons, mainly oil, gas, condensates and others,is today carried out in very diverse environments and in particular inoffshore sites, underwater sites or else in sites experiencing coldweather periods. These diverse environments can often result insignificant cooling of the extracted fluids in contact with the coldwalls of the transportation pipes.

Extracted fluids (or produced fluids or production fluids) is understoodto mean the fluids comprising oil, gases, condensates, water andmixtures thereof. Oil is understood to mean, within the meaning of thepresent invention, crude oil, that is to say unrefined oil, originatingfrom a deposit.

Gases is understood to mean, within the meaning of the presentinvention, crude natural gases, that is to say untreated gases,extracted directly from a deposit, such as, for example, hydrocarbons,such as methane, ethane, propane or butane, hydrogen sulfide, carbondioxide and other compounds which are gaseous under the extractionconditions, and also the mixtures thereof. The composition of theextracted natural gas varies considerably depending on the wells. Thus,the gas may comprise gaseous hydrocarbons, water and other gases.

For the purposes of the present invention, the term “condensates” meanshydrocarbons of intermediate density. Condensates generally comprisemixtures of hydrocarbons which are liquid under the extractionconditions.

It is known that these production fluids usually include an aqueousphase, in a greater or lesser amount. The origin of this aqueous phasemay be endogenous and/or exogenous to the underground reservoircontaining the hydrocarbons, the exogenous aqueous phase generallyoriginating from injection of water, also known as “injection water”.

The depletion of the sites discovered in the past is often nowadaysleading the oil and gas industry to extract, in particular on new sites,from increasingly great depths, on offshore sites and with ever moreextreme weather conditions.

On offshore sites in particular, the pipes for transportation of thefluids produced are often positioned on the seabed, at ever greaterdepths, where the temperature of the seawater is often less than 15° C.,more often less than 10° C., indeed even close to or equal to 4° C.

Similarly, it is common to find extraction sites located in geographicalregions where the air and/or the surface water can be at relatively coldtemperatures, typically below 15° C., indeed even below 10° C. In pointof fact, at such temperatures, the produced fluids undergo significantcooling during their transportation. This cooling can be furthermagnified in the case of a shutdown or a slowdown in production, inwhich cases the contact time between the produced fluids and the coldwalls of the pipe can increase, often considerably.

One of the disadvantages directly related to a more or less suddenlowering of the temperatures of the produced fluids is the formation ofclathrates, also known as hydrate crystals, gas hydrates or more simplyhydrates. The risk of formation of such hydrates in production fluidsand in particular during oil, gas and condensate extraction isproportionately greater the lower the temperature of the productionfluids and the higher the pressure of these fluids.

These clathrates are solid crystals (similar to those of water in theice form) formed by water molecules, also called “hosts”, around one ormore gas molecules, also called “guests”, such as methane, ethane,propane, butane, carbon dioxide or hydrogen sulfide.

The formation and growth of these crystals are usually induced by a dropin the temperature of the production fluids which exit hot from thegeological reservoirs which contain them and which enter a cold region.These crystals can grow more or less rapidly and agglomerate and cancause pluggings or blockages of the production pipes, of the pipes fortransportation of the hydrocarbons (oil, condensates, gas), of thegates, valves and other elements liable to be completely or at leastpartially blocked.

These pluggings/blockages can lead to losses in production of oil,condensates and/or gas, resulting in significant, indeed even verysubstantial, economic losses. This is because these pluggings and/orblockages will have the consequence of a decrease in the productionoutput, indeed even a shutdown of the production unit. In the event ofblockage, the search for the region of the blockage and its removal willresult in a loss of time and of profit for this unit. These pluggingsand/or blockages can also lead to malfunctions with regard to safetyelements (for example safety valves).

These problems of formation and/or agglomeration of hydrates can also beencountered in drilling muds or in completion fluids, during a drillingoperation or a completion operation.

Various solutions have already been proposed or envisaged to reduce,delay or inhibit the formation and/or agglomeration of hydrates. Mentionmay in particular be made, among these, of a first solution whichconsists in dehydrating the production fluid, crude oil or gas, upstreamof the region of the pipe where the temperature promotes the formationof said hydrates. However, this solution is difficult, indeed evenimpossible, to implement under satisfactory economic conditions.

A second approach, which is also very expensive, consists in maintainingthe temperature of the pipe at a temperature greater than thetemperature of formation and/or agglomeration of the hydrates, at agiven pressure.

A third approach, which is frequently used, consists in adding anadditive denoted “thermodynamic hydrate inhibitor” (THI), generally analcohol or alcohol derivative, for example methanol, or glycol, to thefluids produced containing the water/guest gas(es) mixture. It isnowadays commonly recognized that the addition of such an additive makesit possible to shift the thermodynamic equilibrium temperature forformation of the hydrates. In order to obtain an acceptableeffectiveness, approximately 30% by weight of alcohol, with respect tothe amount of water, is generally introduced. However, the toxicity ofthe alcohols or alcohol derivatives and the large amount of additiveused are increasingly leading industrialists to adopt a fourth approach.

This fourth solution consists in adding an additive at low dosage, knownas low dosage hydrate inhibitor (LDHI), to the fluids producedcomprising the water/guest gas(es) mixture. This additive is also knownas hydrate inhibitor and is introduced at a low dosage, generally ofbetween 1% and 4% by weight, with respect to the weight of the water, itbeing understood that greater or smaller amounts are, of course,possible. Two types of hydrate-inhibiting additives are currently known:anti-agglomerants and kinetic hydrate inhibitors.

As indicated above, the formation of hydrates depends mainly on thetemperature and the pressure, and also on the composition of the guestgas or gases. In order to be able to compare the performance of theadditives, use is made of the notion of “sub-cooling” (SC). Sub-coolingis thus defined by the difference between the thermodynamic equilibriumtemperature for formation of the hydrate crystals (T_(eq)), for a givenpressure and a given composition of the hydrate-forming gases and of theaqueous phase, and the temperature of the fluids produced (or extractiontemperature T), according to the following equation: SC=T_(eq)−T.

When the sub-cooling is greater than or equal to 0° C., there is a riskof formation of gas hydrate and this risk increases as the sub-coolingincreases.

Anti-agglomerants are not inhibitors of the formation of hydratecrystals but have the property of dispersing them, which consequentlyprevents said hydrate crystals from agglomerating together. The hydratecrystals, thus dispersed, can no longer plug the pipelines fortransportation of the oil and gas production fluids, thus increasing theproduction, in particular the extraction of oil and gas.

Anti-agglomerants retain their effectiveness even at low temperature.They make it possible in particular to prevent problems of blockage ofthe pipes at temperatures generally of 15° C. below the minimumtemperature at which the hydrate crystals form, for a given pressure.

Kinetic hydrate inhibitors, for their part, act on the germination andthe growth of the hydrate crystals, delaying by several hours, indeedeven by several days, the formation of the crystals. However, incontrast to anti-agglomerants, kinetic hydrate inhibitors operate withdifficulty at large sub-coolings. This is because, at temperatures ofmore than 10° C. below the minimum temperature at which the hydratecrystals form for a given pressure (SC≥10° C.), the effectiveness of thekinetic hydrate inhibitors is reduced.

In other words, at these sub-cooling levels, the time for appearance ofthe crystals is sufficiently short for them to appear, thus increasingthe pressure loss in the pipes for transportation of the oil and gasproduction fluids.

The document CN104357034 discloses a mixture of two homopolymers(poly(vinylpyrrolidone) and poly(vinylcaprolactam)) associated withpropylene glycol. This mixture exhibits kinetic hydrate inhibitorproperties. However, a relatively significant foaming of this mixture isobserved under the conditions of use. In addition, the polymers of thismixture result in a cloud point at a relatively low temperature, whichcan in particular prove to be insufficient during injections under hotconditions.

There consequently remains a real need to develop additives which makeit possible to delay the formation of hydrates (kinetic hydrateinhibitors), which are even more effective and in particular which makeit possible to operate at sub-coolings of greater than 10° C., betterstill of greater than 12° C., more advantageously of greater than 13°C., more preferably of greater than 15° C. In other words, there remainsa real need for kinetic hydrate inhibitors which exhibit induction times(times for formation of the hydrates) which are as long as possible.

SUMMARY OF THE INVENTION

Another objective of the present invention consists in providing akinetic hydrate inhibitor which is effective under the normal conditionsof use, that is to say for a dosage typically of between 0.1% and 10% byweight, with respect to the total weight of the aqueous phase in aproduction fluid. Yet another objective is to provide a kinetic hydrateinhibitor which is not very toxic to the environment but also not veryexpensive and easy to produce.

Another objective of the invention is to provide a kinetic hydrateinhibitor with a higher cloud point than those known from the prior art.Yet another objective is to provide a kinetic hydrate inhibitor whichproduces only slight foaming or foaming which is at least substantiallyreduced, with respect to that observed with the hydrate inhibitors ofthe prior art.

It has now been discovered, surprisingly, that compositions comprisingmixtures of specific polymers make it possible to completely or at leastpartially satisfy the abovementioned objectives, and in particular makeit possible to behave as kinetic hydrate inhibitors exhibitingrelatively long induction times, and in particular longer inductiontimes than those observed with the known kinetic hydrate inhibitors ofthe prior art, this being the case for relatively great sub-coolings.These polymer compositions are in addition shown to be environmentallyfriendly and easy to prepare with entirely reasonable production costs.

Other objectives, characteristics, aspects and advantages of theinvention will become even more clearly apparent on reading thedescription and examples which follow. In that which follows and unlessotherwise indicated, the limits of a range of values are included inthis range, in particular in the expressions “of between . . . and . . .” and “ranging from . . . to . . . ”.

Thus, and according to a first aspect, the present invention relates toa composition comprising:

-   -   a) at least one copolymer, at least one of the repeat units of        which comprises at least one amide functional group,    -   b) at least one polyether with a weight-average molecular weight        (Mw) of greater than 60 g·mol⁻¹, preferably of greater than 100        g·mol⁻¹, and    -   c) optionally, but preferably, at least one organic solvent.

The copolymer, at least one of the repeat units of which comprises atleast one amide functional group, is a copolymer, the amide functionalgroups of which are branched on the polymer chain (“pendant” amidefunctional groups). The nitrogen atoms of said amide functional groupscan be substituted, and are preferably substituted, more preferablymonosubstituted, more preferentially disubstituted. The substituents areidentical or different and are, independently of one another, chosenfrom the hydrogen atom and aliphatic groups comprising from 1 to 30carbon atoms, preferably from 1 to 8 carbon atoms, more preferably from1 to 4 carbon atoms, and optionally comprise 1, 2, 3 or 4, preferably 1or 2, heteroatoms, independently chosen from oxygen, nitrogen andsulfur.

The substituents of the disubstituted amide functional groups can also,and according to another embodiment of the present invention, form ahydrocarbon or heterohydrocarbon ring comprising from 4 to 7 carbonatoms and optionally comprising 1, 2, 3 or 4, preferably 1 or 2,heteroatoms independently chosen from oxygen, nitrogen and sulfur,preferably with a maximum of two heteroatoms in the ring, it beingpossible for the ring itself to be substituted by one or more saturated,linear or branched, alkyl chains comprising one or more heteroatomschosen, independently of one another, from oxygen, nitrogen and sulfur,or a combination of these groups with the heterohydrocarbon ringcomprising from 4 to 7 carbon atoms. Such monomers are, for example,described in detail in Patent Applications US2017321050 andUS2017321108.

According to another embodiment of the present invention, when thenitrogen atoms of the pendant amide functional groups are disubstituted,the two substituents can form, together and with the nitrogen atom whichbears them, a ring and can optionally form a lactam with the amidesequence.

The substituents of the nitrogen atoms of the pendant amide functionalgroups can also comprise one or more nitrogen atom(s), preferably onenitrogen atom. This or these substituent nitrogen atom(s) of thenitrogen atoms of the pendant amide functional groups may also havereacted with one or more alkylating agent(s), so as to form an ammoniumcation, it being possible for the anion to be chosen from all the anionsknown to a person skilled in the art and in particular from halides (forexample chloride or bromide), sulfonates (for example methanesulfonateor para-toluenesulfonate), sulfates (for example methyl sulfate or ethylsulfate), carbonates (for example methyl carbonate), and others.

Copolymer is understood to mean, in this invention, a polymer resultingfrom the polymerization of two, three or more different monomers. Inparticular, terpolymer is understood to mean, in the present invention,a polymer resulting from the polymerization of three different monomers.

The copolymers which can be used in the context of the present inventioncan be block or graft, random, periodic or statistical copolymers,preferably of low molecular weight. Low molecular weight is understoodto mean a weight of between 1000 and 5000 atomic mass units (amu) andpreferably between 1500 and 4000 amu.

According to yet another embodiment of the invention, the monomers whichcan be used to form the copolymers with monomers having an amidefunctional group can be chosen from monomers comprising an aminefunctional group. These amine functional groups can be primary (—NH₂),secondary (—NHR_(a)) or tertiary (—NR_(a)R_(b)) amines, preferablysecondary or tertiary amines. The substituent R_(a) and R_(b) radicalsof the secondary or tertiary amines can be identical or different and bechosen, independently of each other, from saturated or partiallyunsaturated, linear or branched, hydrocarbon chains comprising from 1 to30 carbon atoms, preferably from 1 to 20 carbon atoms, more preferablyfrom 1 to 8 carbon atoms.

The R_(a) and R_(b) radicals can optionally, and with the nitrogen atomwhich bears them, form a heterohydrocarbon ring comprising from 3 to 8,preferably from 4 to 7, ring members with optionally 1, 2, 3 or 4heteroatoms independently chosen from oxygen, nitrogen and sulfur,preferably with a maximum of 2 heteroatoms in the ring, it beingpossible for the ring to be substituted by one or more entities chosenfrom saturated or partially unsaturated, linear or branched, hydrocarbonchains and from heteroatoms independently chosen from oxygen, nitrogenand sulfur. Such monomers are in particular described in detail in thepublications of Patent Applications US2017321050 and US2017321108.

The R_(a) and R_(b) substituents of the nitrogen atoms of theabovementioned pendant amine functional groups can also comprise one ormore nitrogen atom(s), preferably one (1) nitrogen atom. This or thesesubstituent nitrogen atom(s) of the nitrogen atoms of the pendant aminefunctional groups may also have reacted with one or more alkylatingagent(s), so as to form an ammonium cation, it being possible for theanion to be of any type well known to a person skilled in the art andpreferably chosen from halides (for example chloride or bromide),sulfonates (for example methanesulfonate or para-toluenesulfonate),sulfates (for example methyl sulfate or ethyl sulfate), carbonates (forexample methyl carbonate), and others.

According to one embodiment of the invention, the monomer or monomerswhich can be used to form the copolymers clarified above can be of anytype and are advantageously chosen from the monomers of formula (I):

wherein:

-   -   R represents —H or —CH₃, and    -   R₂ is chosen from the hydrogen atom and an alkyl, alkoxy,        hydroxy, N-alkylaminoalkoxy, N,N-dialkylaminoalkoxy,        hydroxyalkoxy radical, saturated or partially or completely        unsaturated cyclic radical comprising from 3 to 8 ring members,        preferably 4 to 7 ring members, and optionally one or more        identical or different heteroatoms which are chosen from oxygen,        nitrogen and sulfur and which are optionally substituted by one        or more groups chosen from alkyl, halogen, carbonyl, hydroxy,        alkoxy, amino, nitro and cyano.

The monomers of formula (I) can, for example and nonlimitingly, bechosen from acrylic acid, alkyl acrylates, N-alkylaminoalkyl acrylatesand N,N-dialkylaminoalkyl acrylates, and also their correspondingquaternary alkyl halides, in particular chlorides, hydroxyalkylacrylates, methacrylic acid, alkyl methacrylates, N-alkylaminoalkylmethacrylates and N,N-dialkylaminoalkyl methacrylates, and also theircorresponding quaternary alkyl halides, in particular chlorides,hydroxyalkyl methacrylates, and others, and also the mixtures of two ormore of them in all proportions.

DETAILED DESCRIPTION OF THE INVENTION

In the present description, the term “alkyl” represents, unlessotherwise indicated, a saturated, linear or branched, hydrocarbonradical comprising from 1 to 10 carbon atoms, preferably from 1 to 6carbon atoms, more preferably from 1 to 4 carbon atoms.

Yet other monomers can participate in the formation of theabovementioned copolymers and, among these, mention may be made,without, however, being limiting, of monomers containing at least onehydroxyl functional group and/or at least one functional group which canbe converted into a hydroxyl functional group. Such monomers are inparticular described in detail in International ApplicationWO2010117660. Mention may very particularly be made, among thesemonomers, of vinyl acetate.

In the composition according to the present invention, the copolymer, atleast one of the repeat units of which comprises at least one amidefunctional group, is a copolymer obtained by polymerization of at leastone monomer comprising a pendant amide functional group, and preferablythe copolymer is a copolymer obtained by polymerization of two or moremonomers comprising a pendant amide functional group, for example chosenfrom substituted or unsubstituted (meth)acrylamides, vinyl monomershaving lactam groups, in particular vinylpyrrolidones orvinylcaprolactams.

According to a preferred embodiment of the present invention, themonomers used for the preparation of the copolymer, at least one of therepeat units of which comprises at least one amide functional group(copolymer a) of the composition of the present invention), are chosenfrom the monomers of vinylcaprolactam (VCap) type and ofvinylpyrrolidone (VP) type.

Copolymers resulting from the copolymerization of at least one vinylmonomer having amide groups and/or cyclic amide groups (lactams) with amonomer containing a hydroxyl functional group and/or a functional groupwhich can be converted into a hydroxyl functional group is understood tomean the copolymers resulting, for example, from the polymerization ofthe monomers of the type of vinylpyrrolidones (VP), vinylcaprolactams(VCap), acrylamides and/or methacrylamides with monomers containing ahydroxyl functional group and/or a functional group which can beconverted into a hydroxyl functional group and in particular themonomers described thus in detail in International ApplicationWO2010117660.

According to one embodiment of the present invention, the copolymers areobtained by copolymerization of vinylcaprolactam (VCap) and/orvinylpyrrolidone (VP) with vinyl acetate and more preferably bycopolymerization of vinylcaprolactam (VCap) with vinyl acetate. Thesecopolymers are known and are commercially available or are easilyprepared from known procedures described in the scientific literature,on the Internet or in patent applications, for example in theabovementioned document WO2010117660.

More particularly, nonlimiting examples of the abovementioned monomersare vinylpyrrolidone (VP), vinylcaprolactam (VCap), acrylamide,methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide,N,N-dialkylacrylamide, N,N-dialkylmethacrylamide,N,N-dialkylaminoalkylacrylamide, N,N-dialkylaminoalkylmethacrylamide,and also the quaternary alkylammonium salts (halides, sulfonates,sulfates, carbonates and others) thereof.

According to one embodiment of the invention, the copolymer a) is acopolymer obtained by copolymerization of monomers of vinylcaprolactam(VCap) type and of vinylpyrrolidone (VP) type. For example, when themonomer of vinylcaprolactam (VCap) type is copolymerized in the presenceof a monomer of vinylpyrrolidone (VP) type, the VCap/VP ratio by weightis advantageously of between 95/5 and 30/70, preferably between 75/25and 50/50 and more preferably still between 60/40 and 50/50.

According to another preferred embodiment of this invention, thecopolymer a) of the composition according to the present invention is aVCap/VOH copolymer obtained by polymerization of N-vinyl-2-caprolactamand vinyl acetate. This copolymerization is advantageously carried outin an appropriate solvent known to a person skilled in the art (forexample butyl glycol), followed by hydrolysis of the polymer in analkaline medium. The VCap/VOH ratio by weight in the final copolymer isof between 30/70 and 95/5, preferably between 60/40 and 85/15 and morepreferably still between 65/35 and 75/25. Mention may be made, forexample, among the copolymers of interest for this invention, of theproduct sold by Ashland Inc. under the trade name Inhibex BIO 800.

The total amount of the copolymer or copolymers a) present in thecomposition of the invention is preferably of between 1% and 50% byweight, more preferably between 5% and 40% by weight and better stillbetween 10% and 30% by weight, with respect to the total weight of thecomposition.

As indicated above, the polyether b) of the composition according to theinvention exhibits a weight-average molecular weight (Mw) of greaterthan 60 g·mol⁻¹, more preferably of greater than 100 g·mol⁻¹. In apreferred embodiment, the polyether b) of the composition according tothe invention has a weight-average molecular weight (Mw) of greater than60 g·mol⁻¹, more preferably of greater than 100 g·mol⁻¹, moreparticularly of greater than 160 g·mol⁻¹, better still of greater than200 g·mol⁻¹, and very particularly of greater than 260 g·mol⁻¹, limitsincluded.

For the purposes of the present invention, it should be understood thatsaid polyether b) may be of any type known to those skilled in the art,optionally functionalized, and in particular a linear polyether, abranched polyether or even a star or hyperbranched polyether. Thepresent invention also encompasses polyethers of “comb” polyether typeor of dendrimer type. A family of such polyethers is described forexample in Application WO2019185490.

According to one embodiment, the polyether b) is a polyether comprisingthe following unit z):

wherein,

-   -   R′ and R″′, which are identical or different, are chosen,        independently of each another, from:        -   the hydrogen atom,        -   a saturated or partially or completely unsaturated, linear,            branched or cyclic, hydrocarbon chain comprising from 1 to            30 carbon atoms, preferably from 1 to 20 carbon atoms, more            preferably from 1 to 10, more preferentially from 1 to 6,            better still from 1 to 5 carbon atoms, limits included,            optionally interrupted by one or more, and preferably one,            oxygen atom(s), and optionally substituted by one or more            radicals chosen from —SR₃, —SOR₃, —SO₂R₃, —SO₃R₃, —S⁺O₃X⁻,            —S⁺R₃R₄X⁻, —P(═O)R₅R₆, —OR₇, —C(═O)R₇, and —C(═O)OR₇,    -   R₇, R₃ and R₄, which are identical or different, represent,        independently of each other, the hydrogen atom and a saturated        or partially or completely unsaturated, linear, branched or        cyclic, hydrocarbon chain comprising from 1 to 30 carbon atoms,        preferably from 1 to 20, more preferably from 1 to 10, more        preferentially from 1 to 6, better still from 1 to 5 carbon        atoms, limits included, optionally interrupted by one or more        oxygen atom(s),    -   R₅ and R₆, which are identical or different, represent,        independently of each other, the hydrogen atom, an —OR₃ radical,        or a saturated or partially or completely unsaturated, linear,        branched or cyclic, hydrocarbon chain comprising from 1 to 30        carbon atoms, preferably from 1 to 20, more preferably from 1 to        10 carbon atoms, more preferentially from 1 to 6, better still        from 1 to 5 carbon atoms, limits included, optionally        interrupted by one or more oxygen atom(s),    -   A represents a saturated or partially or completely unsaturated,        linear, branched or cyclic, hydrocarbon chain comprising from 1        to 10 carbon atoms, preferably from 1 to 6, more preferably from        1 to 5 carbon atoms, limits included, optionally interrupted by        one or more, and preferably one, oxygen atom(s),    -   X⁻ represents an anion chosen from anions of a halogen atom,        such as chlorine, bromine or iodine, a sulfate anion, a        sulfonate anion, a methanesulfonate anion, a carbonate anion, a        hydrogen carbonate anion, an acetate or propionate anion, and    -   n represents an integer of between 1 and 200, preferably between        1 and 100, more preferably between 1 and 60.

According to a preferred embodiment of the present invention, thepolyether b) is a linear or branched polyether represented by thegeneral formula (II) below:

wherein,

-   -   R¹ is chosen from the hydrogen atom and an alkyl radical        comprising from 1 to 6 carbon atoms, preferably from 1 to 4        carbon atoms, preferably the methyl radical and the ethyl        radical,    -   R′ is as defined above,    -   R″ is chosen from:        -   the hydrogen atom,        -   a saturated or partially or completely unsaturated, linear,            branched or cyclic, hydrocarbon chain comprising from 1 to            30 carbon atoms, preferably from 1 to 20, more preferably            from 1 to 10 carbon atoms, more preferentially from 1 to 6,            better still from 1 to 5 carbon atoms, limits included,            optionally interrupted by one or more, and preferably one,            oxygen atom(s), and optionally substituted by one or more            radicals chosen from —SR₃, —SOR₃, —SO₂R₃, —SO₃R₃, —S⁺O₃X⁻,            —S⁺R₃R₄X⁻, —P(═O)R₅R₆, —OR₇, —C(═O)R₇, and —C(═O)OR₇,    -   A, n, R₃, R₄, R₅, R₆, R₇ and X⁻ are as defined above.

According to another embodiment, the polyether b) is a star orhyperbranched polyether comprising more than 2, and for example from 3to 30, preferably from 3 to 20, more preferentially from 3 to 12 units,more preferably from 3 to 6 units and generally 3 or 4 units z) asdefined above. According to one embodiment, the units of formula z) arestar-branched on a central core, it being possible for said central coreto be of any type known to a person skilled in the art and in particulara carbon atom, it being understood that the units of formula z) can beidentical or different in the star or hyperbranched polyether.

When n is strictly greater than 1, it should be understood that the R₁and A radicals can be identical or different, so that the polyether offormula (II) can comprise alternating, block or random sequences.

The polyether can be a homopolymer and can also be a block copolymer,for example composed of two or more blocks, for example chosen fromthose corresponding to the general formula (II) above. The polyether canalso be a statistical copolymer composed of two or more different ethermonomers.

Nonlimiting examples of these polyethers are polyoxymethylene glycol,polyethylene glycol or polypropylene glycol. The polyether can also be apolyalkyl ether, and for example a polyglyceride (mono-, di- and/ortriglyceride) ether, or also a polycycloalkyl ether, for examplepolyfuran, polytetrahydrofuran, and others.

Preference is given, among the polyethers b) of formula (II) above, tothose for which R′ and R″, which are identical or different, are chosen,independently of each other, from the hydrogen atom and an alkyl radicalcomprising from 1 to 4 carbon atoms, preferably the methyl radical andthe ethyl radical, preferably the methyl radical.

Preference is given, according to yet another embodiment, among thepolyethers b) of formula (II) above, to those for which one of the twoR′ and R″ represents the hydrogen atom and the other represents an alkylradical comprising from 1 to 4 carbon atoms, preferably the methylradical and the ethyl radical, preferably the methyl radical.

Examples of polyethers which can advantageously be used in the contextof the present invention comprise, as nonlimiting examples,trimethylolpropane triglycidyl ether, neopentyl glycol diglycidyl ether,poly(ethylene glycol) glycidyl ether, poly(propylene glycol) glycidylether, poly(ethylene glycol) diglycidyl ether, poly(propylene glycol)diglycidyl ether, poly(ethylene glycol) triglycidyl ether,poly(propylene glycol) triglycidyl ether, poly(ethylene glycol)tetraglycidyl ether, poly(propylene glycol) tetraglycidyl ether,glycerol propoxylate triglycidyl ether, poly(ethylene glycol) methylether, poly(ethylene glycol) methyl ether acetate, polyethylene glycoldimethyl ether, polyethylene glycol, polypropylene glycol, polymethyleneglycol, polybutylene glycol, polyethylene-block-poly(ethylene glycol),trimethylolpropane ethoxylate, methoxypolyethylene glycol, glycerolethoxylate, 4-nonylphenyl-polyethylene glycol, glycerol propoxylate,pentaerythritol triacrylate, pentaerythritol propoxylate,pentaerythritol butoxylate, glycerol ethoxylate-co-propoxylate triol,polyalkylene glycol acetic acid, polyalkylene glycol glutaric acid,polyalkylene glycol succinic acid, polyalkylene glycol alkyl ethercarboxylic acid, (and, for example, the products sold under the namesPMD-7002, PMD-7022 and PMD-7042 available from Creative PEGworks:https://www.creativepegworks.com), star polyethers, for example thosesold under the names PSB-480, PSB-483, PSB-466, PSB-469, PSB-4040,PSB-4041, PSB-831, PSB-836, PSB-8021 and PSB-8031 also available fromCreative PEGworks, branched, hyperbranched or dendrimeric polyethers,such as, for example, those sold under the names HBP-121, HBP-122,HBP-123, HBP-124, PDP-301, PDP-302, PDP-303, PDP-311, PDP-312 andPDP-313 and available from Creative PEGworks, or polyethers comprisingglycidyl groups, such as, for example, those sold by Creative PEGworksunder the trade names PLS-280, PLS-279, PLS-278, PLS-277, PSB-281,PSB-282, PSB-2960, PSB-2861, PSB-350, PSB-351, PSB-352, PSB-353,PSB-354, PSB-355, PSB-356, PSB-470, PSB-471, PSB-473, PSB-475, PSB-871,PSB-872 and PSB 874.

Most of the polyethers that can be used in the context of the presentinvention are available from Creative PEGworks; other polyethers arealso available, for example from Sigma Aldrich.

The total amount of the polyether(s) present in the composition of theinvention is generally of between 0.5% and 90% by weight, preferablybetween 0.5% and 50% by weight, preferably between 1% and 30% by weightand more preferably between 5% and 20% by weight, with respect to thetotal weight of the composition.

The composition according to the present invention can optionallycomprise one or more organic solvents. The organic solvents which can beused are advantageously chosen from alkyl alcohols comprising from 1 to4 carbon atoms, glycol ethers and mixtures thereof. According to apreferred aspect, the organic solvent used is a glycol or a glycolmixture and very particularly preferably the organic solvent is butylglycol.

The total amount of organic solvent(s) present in the composition of theinvention is generally of between 30% and 90%, preferably between 50%and 90% and more preferably between 60% and 85%, by weight, with respectto the total weight of the composition.

The composition according to the present invention may also comprise oneor more other additives commonly used in oil and gas production, forinstance those chosen from corrosion inhibitors, top-of-line corrosioninhibitors, kinetic hydrate inhibitors, hydrate anti-agglomerants,mineral deposit inhibitors, demulsifiers, biocides, deoilers,antifoaming agents, paraffin inhibitors and dispersants, asphalteneinhibitors and dispersants, oxygen, hydrogen sulfide or mercaptanscavengers, friction or drag reducers and other colorants, aromas orpreservatives, if necessary or if desired.

The composition according to the present invention can be easilyprepared, for example by mixing the various components, according to anymeans well known to a person skilled in the art, in any order, accordingto the compatibilities and the miscibilities of the components with oneanother. The compositions can thus be prepared by mixing by means of astirrer, at ambient temperature and at atmospheric pressure.

It has been observed, entirely surprisingly, that the compositionaccording to the invention makes it possible to prevent, to limit or atthe very least to delay by several hours, indeed even by several days,the formation and/or the agglomeration of hydrate crystals, inparticular for sub-coolings of greater than 10° C. In addition, it hasbeen observed that the composition of use in the context of the presentinvention often results in a longer induction time than the compositionsor products currently available commercially.

A direct consequence is that the composition according to the presentinvention thus makes it possible to operate at lower temperatures thanthe current temperatures, while increasing the extraction efficiency andin particular the production output of oil and/or gas.

In addition, it has been discovered that this composition is effectiveat low concentrations, for example at dosages of between 0.1% and 10% byweight, preferably between 0.2% and 7% by weight, more preferablybetween 0.2% and 5% by weight and better still between 1% and 4% byweight, with respect to the total weight of the aqueous phase of thefluid liable to form hydrates, and very particularly between 0.2% and4%, typically between 0.2% and 3%, in particular between 1% and 3%, byweight. The composition according to the present invention is also notvery expensive, is easy to produce and is not very toxic.

Thus, and according to another aspect, the present invention relates toa process for preventing, limiting or at the very least delaying, theformation and/or the agglomeration of gas hydrates, comprising a step ofadding a composition as defined above to a fluid liable to formhydrates, as described above in this text, and in particular to aproduction fluid comprising an aqueous phase and one or more gases.

More specifically, the total content of the aqueous phase present in theproduction fluid is generally of between 10% and 90% by weight, withrespect to the total weight of the production fluid, that is to say withrespect to the total weight of the fluids (aqueous phase andhydrocarbons). However, the treatment of fluid having a very highcontent of aqueous phase or containing less than 10% of aqueous phase,indeed even less than 1% of aqueous phase, would not depart from thefield of the invention.

The total content of aqueous phase defined above corresponds to thetotal proportion of aqueous phase initially present in the productionfluid, that is to say in the initial mixture (aqueous phase and theother crude extraction liquids, such as hydrocarbons, condensates, andthe like).

The aqueous phase of the production fluid additionally comprises one ormore dissolved gases liable to form, with water, gas hydrates at a giventemperature and a given pressure. Some of the gases present in theaqueous phase of the production fluid are “guest” gases and generallycomprise methane, ethane, propane, butane, carbon dioxide, hydrogensulfide and mixtures thereof.

The composition according to the invention is added in an amount between0.1% and 10% by weight, preferably between 0.2% and 7% by weight, morepreferably between 0.2% and 5% by weight and better still between 1% and4% by weight, with respect to the total weight of the aqueous phase in aproduction fluid, and very particularly between 0.2% and 4%, typicallybetween 0.2% and 3%, in particular between 1% and 3%, by weight.

The composition may be introduced into the production fluidcontinuously, discontinuously, regularly or irregularly, or temporarily,in one or more portions. The composition is generally introducedupstream of the region at risk of the presence of hydrates, whether atthe surface, at the well head or at the well bottom.

According to another embodiment of the process of the invention, thefluid treated with the composition according to the invention is adrilling mud or a completion fluid and more generally any fluidextracted from the subsoil. In this embodiment, the composition isintroduced into the drilling mud or into the completion fluid, before orduring the injection of the drilling mud or of the completion fluid.

According to one embodiment of the invention, the composition,predominantly present in the aqueous phase of the production fluid, canbe recycled or regenerated according to any method known to a personskilled in the art and in particular, without being limiting and afterseparation of the aqueous phase present in the production fluid, byconcentration or distillation of said aqueous phase.

Finally, another subject matter of the present invention is the use of acomposition as defined above for limiting, delaying, indeed evenpreventing, the formation and/or the agglomeration of hydrates,preferably in a process for extracting oil and/or gas and/orcondensates.

A better understanding of the invention will be obtained in the light ofthe following examples, which are given for illustrative purposes onlyand which are not intended to limit the scope of the invention, definedby the appended claims.

EXAMPLES Example 1

The kinetic effectiveness of different hydrate-inhibiting compositionswas tested on a mixture comprising:

-   -   a gas phase, consisting of 98 mol % of methane and 2 mol % of        propane; and    -   an aqueous phase comprising a 1 g·l⁻¹ NaCl solution.

The tests were carried out at a pressure of 135 bar (13.5 MPa), apressure value which is characteristic of the extraction conditionswhere a risk of hydrate formation exists. The equilibrium temperature ofthis mixture at 135 bar (13.5 MPa) is approximately 19.5° C. In otherwords, at 135 bar (13.5 MPa), the gas hydrates form when the temperaturebecomes less than or equal to 19.5° C.

The tests are carried out in a mechanically stirred celltemperature-controlled by a jacket. The cell is cylindrical in shapewith an internal volume of approximately 292.6 cm³ (149 mm in height for50 mm in diameter). It is made of steel resistant to 200 bar (20 MPa)and is protected by a valve. The working pressure is provided by anAG-30 gas booster from Haskel. The cell comprises instruments in orderto be able to continuously monitor the internal pressure, the stirringtorque and the temperature.

In order to carry out the evaluations of the different products, 250 cm³of aqueous phase containing the additive to be evaluated, or withoutadditive (reference), are first introduced into the cell, under vacuumby suction. After equilibrating the temperature at 19.5° C., the gasmixture is charged, with stirring, to the cell until a stable pressureof 135 bar (13.5 MPa) is obtained.

The assembly is subsequently heated to and maintained at 30° C. for 24hours in order to erase the thermal history of the mixture and is thenbrought down, at the rate of 0.2° C./min, to the temperaturecorresponding to the targeted sub-cooling (in this instance 8.5° C. and4.5° C. for respective sub-coolings of 11° C. and 15° C.).

The kinetic effectiveness of the hydrate-inhibiting compositions ismeasured at different sub-coolings (11° C. and 15° C.) but also atdifferent dosages. The dosage corresponds in this instance to the amount(weight) of hydrate-inhibiting composition introduced into the aqueousphase, with respect to the weight of the water.

The kinetic performance of the hydrate-inhibiting compositions isdetermined by the measurement of the delay time to the formation of thehydrate crystals. This time, also known as induction time, is expressedin hours or in days. In other words, the longer the induction time, themore effective the hydrate inhibitor.

In this instance, this time is measured from the moment when thetemperature in the cell reaches the target temperature of the testcorresponding to the sub-cooling studied (8.5° C. and 4.5° C. forrespective sub-coolings of 11° C. and 15° C.) and the pressure in thecell has stabilized. The final point for measuring the induction timecorresponds to the start of formation of the hydrates. It is located onthe curve of pressure as a function of the time by the point where thepressure begins to fall in the cell (fall in pressure corresponding tothe consumption of gas in order to form solid hydrates) and confirmed byan increase in the torque of the stirrer (viscosification of the medium,which becomes loaded with solid) and possibly a very slight exothermicpeak on the temperature curve.

The composition A, according to the invention, and the comparativecompositions B and C were prepared by mixing the different components,the amounts of which are expressed in Table 1 below.

Unless otherwise indicated, all the amounts are shown as percentage byweight, with respect to the total weight of the composition.

TABLE 1 Composition A Composition B Composition C (invention)(comparative) (comparative) PVP/PVCap 1:1^((a)) 20% 30% — PPG 400^((b))10% — 30% 2-Butoxyethanol 70% 70% 70% ^((a))Vinylpyrrolidone(VP)/Vinylcaprolactam (Vcap) 1:1 copolymer. ^((b))Polypropylene glycolwith a molecular weight of 400 g · mol⁻¹.

The kinetic effectiveness of the hydrate-inhibiting compositions, for asub-cooling of 11° C., is evaluated for a dosage of 1% by weight foreach of the compositions A (invention) and B and C (comparative). Eachof the test compositions is introduced into the aqueous phase and theexperiment is carried out as described above.

The kinetic performance of these compositions, characterized by theinduction time, was measured twice, and the mean of these measurementsis expressed in Table 2 below.

TABLE 2 Results for a sub-cooling of 11° C. Composition A Composition BComposition C (invention) (comparative) (comparative) Induction time 168hours 72 hours 30 hours Dose = 1%

The above results show that, for a sub-cooling of 11° C., thecompositions of the present invention are more effective than thecomparative compositions. This is because, in the composition accordingto the present invention where, when thevinylcaprolactam/vinylpyrrolidone copolymer is in a mixture with apolyether (composition A), 168 hours (for a dosage of 1% by weight) areneeded to see the appearance of gas hydrates.

By way of comparison, the composition C, which comprises only thesolvent and the same polyether, delays the appearance of the hydrates byonly 30 hours. The composition B, comprising only the solvent and thesame copolymer, makes it possible to delay their formation by only 72hours.

The same tests are subsequently carried out for a greater sub-cooling,now of 15° C. Each of the compositions A (invention) and B and C(comparative) is evaluated, according to the protocol described above,for a dose of 1% of each of the compositions A (invention) and B and C(comparative).

The kinetic performance of these compositions was measured twice, andthe mean of these measurements is expressed in the table below.

TABLE 3 Results for a sub-cooling of 15° C. Composition A Composition BComposition C (invention) (comparative) (comparative) Induction time 6hours 3 hours 0.75 hours Dose = 1%

These results lead to similar conclusions. At a dosage of 1% by weight,the comparative composition B delays the formation of gas hydrates byonly 3 hours, whereas the composition according to the invention(composition A) delays this formation by 6 hours.

An advantage is thus clearly established with respect to the prior art,in that the composition according to the present invention results in alonger induction time for greater sub-coolings (15° C.) than thatobserved with the compositions of the prior art. It is thus possible towork at lower temperatures than the current temperatures whileincreasing the production output of oil and/or gas.

Example 2

The objective of the measurement of the cloud point temperature is todetermine if the hydrate-inhibiting composition can be injected into theline transporting the fluids (water, gas, condensate, oil) when they arestill hot, without causing deposition or the risk of blockage.

The composition D, according to the invention, and the comparativecomposition E (in accordance with the teaching of Patent CN104357034)were prepared by mixing the different components, the amounts of whichare expressed in Table 4.

Unless otherwise indicated, all the amounts are shown as percentage byweight, with respect to the total weight of the composition.

TABLE 4 Composition D Composition E (invention) (comparative) PVP/PVCap1:1^((a)) 66% — PVCap^((b)) — 20% PVP 10K^((c)) — 40% PPG 400^((d)) 33%40% ^((a))Vinylpyrrolidone (VP)/vinylcaprolactam (Vcap) 1:1 copolymer.^((b))Vinylcaprolactam polymer. ^((c))Vinylpyrrolidone polymer with amolecular weight of 10 000 g · mol⁻¹. ^((d))Polypropylene glycol with amolecular weight of 400 g · mol⁻¹.

Two aqueous solutions having 1 g and 30 g of sodium chloride (NaCl) perliter are prepared at 20° C. Starting from these solutions, for eachcomposition D and E, 1% by weight solutions in solutions having 1 g and30 g of NaCl per liter are prepared in test tubes. The kinetic hydrateinhibitor solutions are placed in a thermostatically controlled chamberand the temperature is increased in stationary phases of 5° C. startingfrom 20° C. For each stationary phase, the temperature is kept constantfor 1 h. At 20° C., all the solutions are clear.

The cloud point is determined visually when a cloudiness appears in thesolution and is expressed in Table 5 below.

TABLE 5 Composition D Composition E (invention) (comparative) Salinityof the solution 1 g · l⁻¹ 30 g · l⁻¹ 1 g · l⁻¹ 30 g · l⁻¹ Cloud point (°C.) 75° C. 70° C. 45° C. 40° C.

It clearly emerges from these measurements that the compositionaccording to the present invention exhibits a higher cloud point thanthe composition according to the prior art. The composition according tothe present invention can thus be injected into the line transportingthe fluids (water, gas, condensate, oil) at higher temperatures than thecurrent temperatures, which represents a major industrial advantage.

Example 3

The objective of the measurement of the foaming power is to determine ifthe hydrate-inhibiting composition can be injected into the linetransporting the fluids (water, gas, oil, condensate) withoutinterfering with or while interfering to a limited extent with thedownstream operations for treatment of the fluids. This is because theseoperations comprise in particular one or more stages of gas/liquidseparation, which stage can be rendered difficult to carry out in theevent of excessive foaming, it being possible for more or less largeamounts of liquid to be entrained with the gas.

The foaming power of the composition is determined by comparing thecompositions D and E of the preceding example, which were mixedbeforehand with 2-butoxyethanol (70% of solvent and 30% of formulation).100 ml of an aqueous solution having 1 g of NaCl per liter are prepared,which are introduced into a 1 liter graduated measuring cylinder.

The solution is sparged with molecular nitrogen introduced by a sinteredglass of porosity 2 at a flow rate of 2.8 l·min⁻¹ at 20° C. 1% byweight, with respect to the weight of water, of the solvent-containingcomposition to be tested is then rapidly introduced into the measuringcylinder and the sparging is maintained for 2 minutes. With thecomposition of the invention (D), the formation of 100 ml of foam isobserved during the 2 minutes of sparging, then this foam disappears in3 seconds. With the comparative composition (E), more than 900 ml offoam are formed in 20 seconds, then disappear in 30 seconds after thehalting of the sparging.

An advantage with respect to the prior art is thus clearly established,in that the composition according to the present invention exhibits alower foaming power during its injection into the line transporting thefluids water, gas, condensate, oil.

Example 4

The kinetic effectiveness of different hydrate-inhibiting compositionswas tested on mixtures according to the same procedure described indetail in Example 1.

The kinetic effectiveness of different hydrate-inhibiting compositionswas tested on a mixture comprising:

-   -   a gas phase, consisting of 98 mol % of methane and 2 mol % of        propane, and    -   an aqueous phase comprising a 1 g·l⁻¹ NaCl solution.

The tests were carried out at a pressure of 129 bar (12.9 MPa) at 30°C., a pressure value which is characteristic of the extractionconditions where a risk of hydrate formation exists.

The assembly is subsequently heated to and maintained at 30° C. for 24hours in order to erase the thermal history of the mixture and is thenbrought down, at the rate of 0.2° C.·min⁻¹, to the temperaturecorresponding to the targeted sub-cooling (10° C., 11° C., 13° C., 14°C. and 15° C.).

The assembly is first maintained at the sub-cooling 10° C. for 72 hours.If, at the end of the time on this temperature stationary phase, thehydrate has not formed, then the temperature is brought down to 11° C.of sub-cooling and maintained for 24 hours. If, at the end of 24 hours,the hydrate has not formed, then the assembly is brought down to 13° C.for 24 hours, then to 14° C. of sub-cooling for 24 hours and finally to15° C. of sub-cooling, and so on, until the hydrate is formed.

The compositions F and G according to the invention were prepared bymixing the different components, the amounts of which are expressed inTable 6 below, in which, and unless otherwise indicated, all the amountsare shown as percentage by weight, with respect to the total weight ofthe composition.

TABLE 6 Composition F Composition G (invention) (invention) PVP/PVCap1:1^((a)) 20% 20% PTHF 250^((b)) 10% — POM^((c)) — 10% 2-Butoxyethanol70% 70% ^((a))Vinylpyrrolidone (VP)/vinylcaprolactam (Vcap) 1:1copolymer. ^((b))Polytetrahydrofuran with a molecular weight of 250 g ·mol⁻¹. ^((c))Polymethylene glycol.

The kinetic effectiveness of the hydrate-inhibiting compositions isevaluated for a dosage of 1% by weight for each of the compositions Fand G. Each of the compositions to be tested is introduced into theaqueous phase and the experiment is carried out as described above.

For each sub-cooling, the kinetic performance of these compositions isexpressed in Table 7 below, characterized by the induction time. Theinduction time corresponds to the time which the hydrate takes to formonce the desired sub-cooling stationary phase is reached. If the hydratehas not formed during the time for which the system is maintained at astationary phase, then the comment “no hydrate formation” appears inTable 7.

TABLE 7 Dose = 1% by weight Composition F Composition G 10° C. ofsub-cooling No hydrate formation No hydrate formation (stationary phaseof 72 hours) 11° C. of sub-cooling No hydrate formation No hydrateformation (stationary phase of 24 hours) 13° C. of sub-cooling Nohydrate formation Formation after 5 (stationary phase of 24 hours hours)14° C. of sub-cooling Formation after 13 — (stationary phase of 24 hourshours)

At a dosage of 1% by weight, the compositions F and G according to thepresent invention delay the formation of gas hydrates at 10° C. and 11°C. respectively by at least 72 hours and 24 hours. The composition Fdelays the formation of gas hydrates at 14° C. of sub-cooling by 13hours and the composition G delays by 5 hours the formation of gashydrates at 13° C. of sub-cooling.

1. A composition comprising: a) at least one copolymer, at least one ofthe repeat units of which comprises at least one amide functional group,b) at least one polyether with a weight-average molecular weight (Mw) ofgreater than 60 g·mol⁻¹, and c) optionally at least one organic solvent.2. The composition as claimed in claim 1, wherein the copolymer, atleast one of the repeat units of which comprises at least one amidefunctional group, is a copolymer, the amide functional groups of whichare branched on the polymer chain (“pendant” amide functional groups),the nitrogen atoms of said amide functional groups can be substituted.3. The composition as claimed in claim 1, wherein the monomer ormonomers which can be used to form the copolymers a) are chosen from themonomers of formula (I):

wherein: R represents —H or —CH₃, and R₂ is chosen from the hydrogenatom and an alkyl, alkoxy, hydroxy, N-alkylaminoalkoxy,N,N-dialkylaminoalkoxy, hydroxyalkoxy radical, saturated or partially orcompletely unsaturated cyclic radical comprising from 3 to 8 ringmembers, and optionally one or more identical or different heteroatomswhich are chosen from oxygen, nitrogen and sulfur and which areoptionally substituted by one or more groups chosen from alkyl, halogen,carbonyl, hydroxy, alkoxy, amino, nitro and cyano.
 4. The composition asclaimed in claim 1, wherein the copolymer, at least one of the repeatunits of which comprises at least one amide functional group, is acopolymer obtained by polymerization of at least one monomer comprisinga pendant amide functional group.
 5. The composition as claimed in claim1, wherein the polymer, at least one of the repeat units of whichcomprises at least one amide functional group, is a polymer obtained bypolymerization of one or more monomers chosen from vinylpyrrolidone(VP), vinylcaprolactam (VCap), acrylamide, methacrylamide,N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide,N,N-dialkylmethacrylamide, N,N-dialkylaminoalkylacrylamide,N,N-dialkylaminoalkylmethacrylamide, and also the quaternaryalkylammonium salts thereof.
 6. The composition as claimed in claim 1,wherein the total amount of the copolymer or copolymers a) is of between1% and 50% by weight, with respect to the total weight of thecomposition.
 7. The composition as claimed in claim 1, wherein thepolyether b) is represented by the formula (II) below:

wherein, R₁ is chosen from the hydrogen atom and an alkyl radicalcomprising from 1 to 6 carbon atoms, R′ and R″, which are identical ordifferent, are chosen, independently of each other, from the hydrogenatom and a saturated or partially or completely unsaturated, linear,branched or cyclic, hydrocarbon chain comprising from 1 to 10 carbonatoms, limits included, optionally interrupted by one or more oxygenatom(s), A represents a saturated or partially or completelyunsaturated, linear, branched or cyclic, hydrocarbon chain comprisingfrom 1 to 10 carbon atoms, limits included, optionally interrupted byone or more oxygen atom(s), and n represents an integer of between 1 and200.
 8. The composition as claimed in claim 1, wherein the polyether isa homopolymer or a block copolymer, composed of two or more blocks, or astatistical copolymer composed of two or more different ether monomers.9. The composition as claimed in claim 1, wherein the total amount ofthe polyether(s) is of between 0.5% and 90% by weight, with respect tothe total weight of the composition.
 10. The composition as claimed inclaim 1, wherein said at least one organic solvent is chosen from alkylalcohols comprising from 1 to 4 carbon atoms, glycol ethers and mixturesthereof.
 11. A process for preventing, limiting or delaying theformation and/or the agglomeration of gas hydrates, comprising a step ofadding a composition as defined in claim 1 to a mixture having acomposition liable to form hydrates.
 12. The process as claimed in claim11, wherein the composition according to the invention is added in anamount between 0.1% and 10% by weight, with respect to the total weightof the aqueous phase of the fluid liable to form hydrates.
 13. Theprocess as claimed in claim 11, wherein the composition is introducedinto the fluid liable to form hydrates continuously, discontinuously,regularly or irregularly, or temporarily, in one or more portions. 14.The process as claimed in claim 11, wherein the fluid treated with thecomposition according to the invention is a drilling mud or a completionfluid or a fluid extracted from the subsoil.
 15. The use of acomposition as claimed in claim 1 for limiting, delaying or preventingthe formation and/or the agglomeration of hydrates.